The present invention relates, in general, to the field of data transducers for magnetic recording. More particularly, the present invention relates to a variable width flat tape head for bi-directional contact recording and method for making the same.
The effectiveness of contact recording in magnetic tape drives depends, to a large extent, on the spacing between the head and the tape medium and, as a consequence, conventional contact recording tape heads often contain a complex contoured surface with which to contact the tape. This contoured surface is comparatively expensive to manufacture and therefore adds significantly to the overall cost of the head. With contoured tape heads, however, as the tape speed increases, air can be entrained at the edges with resultant signal loss. In an effort to ameliorate this condition, bleed slots (whether transverse or longitudinal) may be cut into the head to reduce the effect of this boundary layer of air. However, this only further adds to the cost of head production by adding additional manufacturing steps.
An alternative head design is what is known generally as a xe2x80x9cflat headxe2x80x9d. These designs are relatively well understood, and it is known that they can provide significant advantages over traditionally designed contoured tape heads. Moreover, a flat head design is simpler to produce and significantly reduces manufacturing costs by eliminating the contouring processes. However, all flat head designs described to date have been of a single width.
The physics surrounding such single width flat head designs have been described, inter alia, by Dr. Sinan Muftu in a number of monographs on the subject. See for example: The Self Acting, Subambient Foil Bearing in High Speed, Contact Tape Recording with a Flat Head, Muftu, S. and Hinteregger, H., Tribology Transactions (Feb. 11, 1997); Contact Tape Recording with a Flat Head Contour, Hinteregger, H., and Muftu, S., IEEE Transactions on Magnetics, Vol. 32. No. 5, September 1996; Flat Heads For Contact Tape Recording: Measurements of Performance Insensitivity to Speed, Tension, Stiffness, and wrap Variations, Hinteregger, H., and Muftu, S., Proceedings of the 10th Symposium on Information Storage and Processing Systems, Santa Clara, Calif. Jun. 28-30, 1999.
Regardless of the design chosen, wear of both the tape and the head will obviously occur at the tape-to-head interface and this wear is directly proportional to the area in actual physical contact. Further, with the use of thin-film wafer materials for the production of more advanced tape heads, the wafer substrate is often a wear resistant material (e.g. ceramic or aluminum-titanium carbide xe2x80x9cAlxe2x80x94TiCxe2x80x9d) and wear and damage of the tape can be a significant issue.
The variable width flat tape head for bi-directional contact recording and method of making the same disclosed herein overcomes many of the limitations of conventional single width flat head designs by incorporating the advantages of variable width to aid in providing overall performance enhancements and cost effective manufacturability. In this regard, the variable width bi-directional flat head of the present invention affords all of the distinct advantages of a conventional single width flat head, while providing important advantages over those older designs in the minimization of tape wear together with significant decreases in manufacturing costs associated with the creation of a bi-directional tape head.
As disclosed herein, the variable width flat tape head design of the present invention reduces manufacturing costs by eliminating the requirement to utilize additional wafer space for physically supporting the tape. In addition, this design eliminates the need for the bonding of xe2x80x98wear padsxe2x80x99 adjacent to the device active region to physically support the tape across its entire width to provide uniform contact with the tape during operation. The variable width flat head design of the present invention effectively reduces the area of contact between the head and the tape, thereby reducing wear and potential damage to the tape during operation. Specifically, the design disclosed herein exhibits many significant advantages over both traditionally contoured tape heads and single width flat heads and the flat head effect is used in this design only over the active elements of the head, thus reducing potential tape damage.
Among the advantages of the variable width bi-directional flat tape head design of the present invention are robust performance over a wide range of tape speeds. In this regard, the design affords an actual decrease in tape-to-head spacing at increasing tape speeds (from xcx9c50 inches per second (xe2x80x9cipsxe2x80x9d) to 500 ips or more) in contrast to traditionally contoured tape heads where the tape head spacing actually increases with increasing tape speeds. Moreover, the head design of the present invention is scalable with the increasing tape speeds required to provide for faster data transfer rates.
The design disclosed herein further provides for more robust performance at relatively low tape tensions with acceptable tape-to-head spacing required for contact recording being achieved at only about 1.0-3.0 oz. These lower tape tensions lead to less tape wear, less pole tip recession (xe2x80x9cPTRxe2x80x9d) or differential wear over the device region and substrate and, ultimately to less power being required in the tape transport motors.
The outriggers forming a part of the specific embodiment of the invention illustrated herein, serve to accurately control the wrap angle of the tape about the head in order to essentially achieve a xe2x80x9cflat head effectxe2x80x9d at relatively low wrap angles of 0.1 to xcx9c5.0 degrees. Beneficially, these low wrap angles further provide less wear to the tape medium and the ability to provide a more simplified tape path when used in a tape drive application. Further, the physics of the variable width flat head provided herein scale with the tape width and a single head design can be used in conjunction with outriggers of varying length in conjunction with a variety of media widths to achieve many possible different form factors while still providing acceptable tape-to-head spacing and potential backwards compatibility.
Further, the variable width bi-directional flat head design of the present invention is robust with respect to head length changes and can accommodate many active elements within a given length while still providing excellent tape-to-head spacing. The head profile provided will also operate effectively in conjunction with a wide variety of tape types (critical parameters include: tape thickness, Young""s modulus, tape tension and the like) as opposed to conventional contoured heads which must be individually designed for a given tape medium having particularly defined characteristics in order to minimize entrained air which could lead to signal loss or excessive tape damage. Consequently, it can be used in conjunction with a number of differing media and a single head design (as opposed to many differing designs) is all that is needed in order to accommodate them.
Other known advantages of the present design include the fact that there is less head area in actual contact with the tape, leading to a reduction in potential wear and damage of the tape and head as compared to single-width flat heads and contoured heads. This, naturally, leads to longer tape life. Moreover, the xe2x80x9cflat head effectxe2x80x9d serves to stabilize the tape over the region of, and between, the active clusters. This allows for fewer tape disturbances such as flutter and lateral tape motion (xe2x80x9cLTMxe2x80x9d) of particular benefit in optical servo applications. In this regard, the design provides an appropriate geometry for the inclusion of an optical sensor to sense optical servo marks on the magnetic side of tape. It further provides for a region within the head structure for the potential inclusion of a lens for detecting optical servo marks on the data tape including those lying in the center of two active clusters at the plane of symmetry.
There are also many manufacturing advantages inherent in the design disclosed herein for a variable width bi-directional flat head which include significant cost reductions due to its simplicity of fabrication and the elimination of many traditionally used processing operations. The magnetoresistive (xe2x80x9cMRxe2x80x9d) read element stripe height may be controlled with a single operation (flat lapping) rather than the multiple steps required in the manufacture of conventional contoured tape heads which require multiple and expensive contour lapping operations with relatively poor yields due to the fact that stripe height and contour shape are interdependent variables. Further, in a particular embodiment, the design of the present invention facilitates the alignment of the head active elements in the two device clusters using a simple fixture rather than expensive optical alignment stations which are currently used in the production of conventional contoured heads. Moreover, the outriggers utilized in the present invention may be easily assembled to precisely control wrap angles necessary to induce the xe2x80x9cflat head effectxe2x80x9d over bi-directional cluster region. Through an efficient use of head wafer real-estate, no wafer space is xe2x80x9csacrificedxe2x80x9d to provide mechanical support to the full width of the tape, as is required in traditional single width flat heads.
Overall, the simplicity of manufacture of the design of the present invention leads to: a reduction in the need for expensive manufacturing or processing capital equipment expenditures; a reduction in processing consumables (e.g. no need for the conventional diamond tape used for contour lapping); a reduction in manufacturing labor; a reduction in total processing time with a concomitant reduction in xe2x80x9cWork-In-Processxe2x80x9d (xe2x80x9cWIPxe2x80x9d) with an increase in head yield due to the simplicity and elimination of operations, especially stripe height control.
Particularly disclosed herein is a variable width flat tape head for bi-directional contact recording. The method for making the same has significant advantages over both traditional contoured tape heads and single width flat heads for contact recording applications. The variable width head and process disclosed herein allows for greater ease of manufacturing, efficient layout of the devices on thin film wafers and provides a significant cost reduction in the production of the head compared to traditionally contoured tape heads. In addition, the present invention reduces unnecessary surface area where the tape contacts the head, thus reducing tape wear and damage that is present in single width flat heads, (where the tape is in contact uniformly across the tape width), thereby providing a concomitant improvement in tape wear and life. In addition, the head of the present invention is simpler and less costly to manufacture than comparable devices with distinct advantages to the MR read element stripe height control process, device alignment and assembly processes, particularly with respect to traditionally contoured tape heads which require more complex and expensive manufacturing operations to form the tape head profile.